Usage:
The Diagnostic Process
System Operation
The PEEC III 3406 Diesel Truck Engine is an electronically-controlled 3406. PEEC III controls fuel rate and timing electronically instead of using flyweights and linkages. The electronics also replaces the mechanical fuel-air ratio control, torque control group, and various adjustment screws.
PEEC III uses several sensors as inputs to control two basic functions: rack and timing. Operation of each of these are similar. PEEC III decides where it wants to position the rack or timing advance. It then varies the voltage to the solenoid (BTM) to move the rack or timing to the desired position. Position sensors tell PEEC III when rack or timing is at the desired position.
Electronic Controls
The electronic controller consists of two main components: the Electronic Control Module (ECM) and the Personality Module. The ECM is the computer which controls the PEEC engine. The Personality Module is the software which controls how the computer behaves. The two must be used together: neither can do anything by itself.
Rack Controls
The rack mechanism on a PEEC III engine is very similar to a mechanical 3406 engine. The fuel injection pump is nearly identical; the rack is moved by a servo valve which receives oil pressure from the fuel injection pump. However, the PEEC III servo spool is moved by a solenoid (BTM) rather than by a linkage controlled by flyweights and springs.
PEEC III determines a "desired rpm" based on the throttle position, vehicle speed, customer specified parameters, and certain diagnostic codes. The PEEC III governor tries to maintain the desired rpm by sensing actual engine speed using the engine speed sensor, then controlling the rack to achieve the desired rpm.
PEEC III RPM Control Logic
To move the rack, PEEC III adjusts the voltage to the rack solenoid (BTM) to increase rack. More voltage results in more rack. PEEC III knows how far the rack went by reading the rack position sensor. PEEC III increases the voltage to the rack solenoid until it senses the rack is in the desired position.
PEEC III Electronic Governor
PEEC III sets certain limits on rack motion. "FRC Rack" is a rack limit based on fuel-air ratio control, for emissions purposes. It works similar to a mechanical engine FARC; when PEEC III senses a higher boost pressure (more air into cylinder), it increases the FRC Rack limit, which allows more fuel into the cylinder. "Rated Rack" is a rack limit based on horsepower of the engine. It is similar to the rack stops and torque springs on a mechanical engine. It provides horsepower and torque curves for a specific engine family and rating. All of these limits are programmed by the factory into the personality module.
Timing Advance Controls
The timing advance mechanism is the same as the 3406 mechanical engine, except the Timing solenoid (BTM), instead of the flyweights, controls timing advance. PEEC III adjusts voltage to the timing solenoid to change timing advance. More voltage results in more timing advance. PEEC III knows how much advance was achieved by reading the timing position sensor. PEEC III simply increases voltage to the timing solenoid until it senses that the timing advance is in the desired position.
PEEC III Timing Advance
Programmable Parameters
Certain parameters that affect PEEC III 3406 Diesel Engine operation may be changed with electronic service tools (either the ECAP or DDT). The parameters are stored in the ECM, and are protected from unauthorized changes by passwords.
These parameters are either "System Configuration Parameters" or "Customer Parameters". System Configuration Parameters are those that effect horsepower family or emissions. Customer Parameters are those that affect cruise control, vehicle speed limits, progressive shifting, horsepower rating within a family, engine protection mode, and PTO operation.
Some parameters may affect engine operation in ways a driver does not expect without adequate training. These may lead to power or performance complaints, even when the engine is performing to specification.
Passwords
"System Configuration Parameters" are protected by factory passwords. Factory passwords are calculated on a computer system available only to Caterpillar dealers. Since factory passwords contain alphabetic characters, only the ECAP may change System Configuration Parameters.
"Customer Parameters" are protected by customer passwords. The customer passwords are programmed by the customer. Either the ECAP or DDT may change customer Parameters (although if a customer programs his password with alphabetic characters using an ECAP, only an ECAP can change Customer Parameters, since the DDT does not have alphabetic characters).
Self-Diagnostics
The PEEC III electronics have some ability to diagnose itself. When a problem is detected, a diagnostic code is generated and the diagnostic lamp is turned on. In most cases, the code is also stored in permanent memory in the ECM.
Codes that represent current faults are called ACTIVE. They indicate that a problem of some kind currently exists. They should always be serviced first. See the section on "Troubleshooting Diagnostic Codes" in this manual for more details.
Codes stored in memory are called LOGGED. Since the problem may have been temporary or may have been repaired since the time it was logged, logged codes don't necessarily mean something needs to be repaired. Instead they are meant to be an indicator of probable causes for intermittent problems. In addition, some logged codes record "events", rather than failures. Codes not requiring passwords to clear are automatically deleted after 100 ECM hours. See the section on "Troubleshooting Diagnostic Codes" in this manual for more details.
PEEC III System Component Diagram
PEEC III Engine Diagram
Electrical Connectors and Functions
Service Tools
The Caterpillar Service Tools for the PEEC III system are designed to help the service technician analyze and locate faults or problems within the system. Their use is required in order to perform sensor calibrations electronically, and to read or change engine parameters. The basic tools have small plug-in modules, called service Program Modules (SPM), to adapt the basic tools to the specific Caterpillar electronic engine application.
The two principle tools are the Electronic Control Analyzer Programmer (ECAP), and the Digital Diagnostic Tool (DDT). Both are able to Communicate with the PEEC III Electronic Control Module to read Diagnostic Codes, to read the various sensor output signals such as engine RPM, rack position, or boost pressure, and to be capable of electronically calibrating the PEEC III sensors.
Both the ECAP (requires PWM adapter) and DDT can measure Pulse Width Modulated (PWM) signals, such as those produced by the Throttle Position Sensor. The ECAP (only) is required when entering Factory Passwords, or for customer passwords containing alpha characters.
There are several adapter cables, breakout "T" cables, probes, etc., that are used with the service tools in order to gain access for measurements of wires carrying voltages and signals. Both heavy duty multimeter and the standard duty multimeter (listed below) are suitable for making the necessary measurements. Other Special Tools include those needed to measure pressure or temperature.
1Refer to Special Instruction Form No. SEHS8742: Using the 8T8697 Electronic Control Analyzer Programmer (ECAP).
2The NEXG4522 Dual SPM will service all 3406 PEEC and 3176 truck engines. The NEXG4522 is a subscription, since it is anticipated that it will be changing at regular intervals.
3Refer to Special Instruction Form SEHS8807: Installation and Use of the 8C9801 Pulse Width Modulated (PWM) Signal Adapter Group.
4Refer to Special Instruction Form No. SEHS9076: Using the 7X6400 Digital Diagnostic Tool (DDT) Group.
5Refer to Special Instruction Form No. SEHS8580.
6Refer to Special Instruction Form No. SEHS8868.
7Refer to Special Instruction Form No. SEHS8740 for using the 8C9700 Rechargeable Portable Printer.
8Refer to Operating Manual Form No. SEHS8834 for using the NEXG4512 Customer Parameter Configuration Aid Service Program Module.
9Refer to Special Instruction Form No. SEHS8833 for installing the 7X1180 Internal Expansion Board in the 8T8697 ECAP Service Tool.
10Refer to Operating Manual Form No. SEHS8741 for using the NEXG4522 Truck Functions Dual Service Program Module.
11Refer to Operating Manual Form No. SEHS8743 for using the NEXG4508 PEEC Service Program Module.
12Refer to Special Instruction Form No. SEHS8907 for using the 1U5470 Engine Pressure Group.
PEEC III Wiring Schematic
